JP4859608B2 - Power unit output shaft - Google Patents

Description

  The present invention relates to an output shaft in a power unit that integrally includes an internal combustion engine and a transmission.

  In the power unit, the rotation of the crankshaft of the internal combustion engine is shifted by the transmission and transmitted to the output shaft, and the rotation of the output shaft protruding from the unit case is transmitted to the drive wheels for rotation.

  Since a large load is applied to the output shaft, a large output shaft manufactured by forging is usually used in order to obtain strength (see, for example, Patent Document 1).

JP 2003-139124 A

The output shaft disclosed in Patent Document 1 is a solid one that is entirely manufactured by forging or the like and has a weight.
Nevertheless, in addition to facilitating positioning by making the diameter of only the bearing portion of the output shaft larger, some weight has been reduced.

  However, there is a limit in strength to reduce the diameter of the output shaft other than the large-bearing part, and there is a slight reduction in weight. The manufacturing equipment for integrally forming the entire output shaft by forging is also enlarged. Equipment costs are also required.

  This invention is made | formed in view of this point, The process which makes it the objective is to provide the output shaft of the power unit which can be manufactured with a small manufacturing apparatus and can be reduced in weight while maintaining intensity | strength.

In order to achieve the above object, the invention described in claim 1 includes a driven case (75) for inputting the power of the internal combustion engine (E) of the power unit (P) through the transmission mechanism (T), and a unit case (P In the output shaft (80) of the power unit (P) that outputs power to the outside of the bearing member members (81, 82) at both ends that are rotatably supported by the unit case (31) via bearings, respectively. The bearing members (81, 82) at both ends are connected by cylindrical members (83), and the driven gear (75) is fitted to one bearing member (81) adjacent to the bearing (86b). The output shaft of the power unit to be worn.

According to a third aspect of the present invention, in the output shaft of the power unit according to the first or second aspect , the unit case (31) is divided into a vertically divided crankcase (31U, 31L) and the crankcase (31L, 31R). Both of the case members (85, 150) connected to both outer sides in the crankshaft direction, and each of the case members (85, 150) has a bearing member (81, 82) at both ends of the output shaft (80) as a bearing. It is supported by (85b, 111b).

According to a fourth aspect of the present invention, in the output shaft of the power unit according to the third aspect , the power unit (P) is mounted on the vehicle with the crankshaft (30) oriented in the front-rear direction, and the crankcase (31U, 31L A through hole (76f) through which the output shaft (80) passes is adjacent to the bearing portion of the transmission shaft (71) that is pivotally supported on the upper and lower crankcases (31U, 31L). (31L).

According to the output shaft of the power unit according to claim 1, the cylindrical member (83) is connected to the bearing members (81, 82) at both ends respectively forged and formed, and the output shaft is configured. Since the driven gear (75) is fitted to the bearing (86b) adjacent to the bearing (86) in 81), the weight can be reduced while ensuring rigidity and strength.
Further, the manufacturing apparatus for forming the small bearing member (81, 82) which is the output shaft (80) can be downsized, and the equipment cost is low.

According to the output shaft of the power unit according to claim 3 , the output shaft (80) is connected to each of the case members (31U, 31L) connected to both outer sides in the crankshaft direction of the vertically divided crankcase (31U, 31L). Since the bearing members (81, 82) at both ends of the shaft are pivotally supported via the bearings (85b, 111b), the load on the crankcase (31L, 31R) is reduced, and the bearing members (81, 82) at both ends are reduced. ) Can be separated from each other so that the cylindrical member (83) can be configured to be long, and a structure in which one distortion of the output shaft (80) hardly affects the other can be achieved.

According to the output shaft of the power unit according to claim 4, a through hole (76f) adjacent to the bearing portion of the transmission shaft (71) is formed in one crankcase (31L) of the vertically divided crankcase (31L, 31R). Since the output shaft (80) passes through the through hole (76f), the output shaft can be brought as close as possible to the transmission shaft (71), and the power unit can be downsized.

Even if the output shaft (80) is brought close to the transmission shaft (71), the transmission shaft (71) is pivotally supported by the crankcase (31L, 31R), whereas the output shaft (80) is supported by the case member (85, 150). ), The rigidity of both bearings can be easily secured and both shafts can be supported well.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
FIG. 1 is a side view showing a state where a vehicle body cover and the like of a rough terrain vehicle 1 mounted with a water-cooled internal combustion engine E according to the present embodiment is mounted, and FIG. 2 is a plan view thereof.
In the present embodiment, the front, rear, left and right are determined based on the state in which the vehicle is directed forward.

  The rough terrain vehicle 1 is a saddle-ride type four-wheel vehicle, and includes a pair of left and right front wheels FW to which low pressure balloon tires for rough terrain are mounted, and a pair of left and right rear wheels RW to which the same balloon tires are mounted. It is suspended before and after the body frame 2.

The body frame 2 is formed by combining a plurality of types of steel materials, and includes a center frame portion 3 on which a power unit P in which an internal combustion engine E and a transmission T are integrally formed in a crankcase 31 is mounted, and the front of the center frame portion 3. the front frame section 4 for suspending a front wheel FW is connected to section, is connected to the rear of the center frame portion 3 consists of a rear frame portion 5 having a seat rail 6 for supporting the sheet 7.

  The center frame portion 3 has a pair of left and right upper pipes 3a bent in the front and rear directions to form approximately three sides, and another pair of left and right lower pipes 3b connected to each other to form a generally rectangular shape in side view. The pipe is configured by connecting cross members.

  A swing arm 9 pivotally supported at the front end is swingably provided on a pivot plate 8 fixed to a portion of the lower pipe 3b that is bent and extended obliquely upward, and the rear portion of the swing arm 9 and the rear frame portion 5 are swingably provided. A rear cushion 10 is interposed therebetween, and a rear wheel RW is suspended from a rear final reduction gear unit 19 provided at the rear end of the swing arm 9.

  A steering column 11 is supported at the center in the width direction of the cross member installed between the front end portions of the left and right upper pipes 3a, and a steering handle 13 is attached to an upper end portion of a steering shaft 12 supported by the steering column 11 so as to be steerable. And the lower end of the steering shaft 12 is connected to the front wheel steering mechanism 14.

The internal combustion engine E of the power unit P is a water-cooled two-cylinder internal combustion engine, and is mounted on the center frame portion 3 in a so-called vertical posture with the crankshaft 30 oriented in the longitudinal direction of the vehicle body.
The transmission T of the power unit P is disposed on the left side of the internal combustion engine E, and an output shaft 80 directed in the front-rear direction projects from the transmission T near the left side. The rotational power of the output shaft 80 is It is transmitted from the front end of the output shaft 80 to the left and right front wheels FW via the front drive shaft 16 and the front final reduction gear unit 17, and from the rear end to the left and right rear wheels via the rear drive shaft 18 and the rear final reduction gear unit 19. Is transmitted to the RW.

  A radiator 27 is supported on the front frame portion 4 of the vehicle body frame 2, and an oil cooler 28 is disposed in front of the radiator 27.

  Referring to FIG. 3 which is a rear view of the power unit P, a crankcase 31 that internally constitutes the internal combustion engine E and the transmission T of the power unit P is an upper crankcase 31U that is divided vertically by a plane including the crankshaft 30. And a lower crankcase 31L.

A cylinder block part 32 formed integrally with two cylinder bores 32c arranged in series is formed on the upper part of the upper crankcase 31U so as to be inclined to the left and extend upward. The cylinder head 33 is overlapped, and the cylinder head cover 34 is put on the cylinder head 33.
On the other hand, an oil pan 35 is attached under the lower crankcase 31L.

  An intake pipe 20 that curves from the right side wall of the cylinder head 33 and extends substantially upward is connected to an air cleaner 22 disposed above the internal combustion engine E with a throttle body 21 in the middle, and the left side wall of the cylinder head 33 An exhaust pipe 23 that is curved and extends rearward is connected to an exhaust muffler 24 attached to the left side of the rear frame portion 5.

  3 and 4, the piston 40 is fitted to the two cylinder bores 32c of the cylinder block 32 so as to be slidable back and forth, and the crank pin 30p between the crank webs 30w and 30w of the crankshaft 30 and the piston 40 A connecting rod 41 is connected to the piston pin 40p to constitute a crank mechanism.

The cylinder head 33 has, for each cylinder bore 32c, a combustion chamber 42 formed facing the piston 40, and an intake port 43 that opens to the combustion chamber 42 and is opened and closed by a pair of intake valves 45 on the right and above. An exhaust port 44 that opens and closes by a pair of exhaust valves 46 extends forward, and a spark plug 47 that faces the combustion chamber 42 is mounted.
The intake pipe 20 is connected to the intake port 43.

The upper end of the intake valve 45 abuts on the intake cam lobe 48i of the cam shaft 48 rotatably supported by the cylinder head 33, and one end of the rocker arm 50 pivotally supported by the rocker arm shaft 49 contacts the exhaust cam lobe 48e of the cam shaft 48. The upper end of the exhaust valve 46 is in contact with the other end of the rocker arm 50.
Therefore, in synchronization with the rotation of the crankshaft 30 by the camshaft 48, the intake valve 45 and the exhaust valve 46 open and close the intake port 43 and the exhaust port 44, respectively, at a predetermined timing.

  For this purpose, the camshaft 48 is fitted with a cam sprocket 48s at the rear, and a timing chain 51 is spanned between the drive sprocket 30s and the cam sprocket 48s fitted near the rear end of the crankshaft 30 (see FIG. 4) and is driven to rotate at half the rotational speed of the crankshaft 30.

The crankshaft 30 is sandwiched between the upper crankcase 31U and the lower crankcase 31L via a plain bearing 52 and is rotatably supported. As shown in FIG. 4, the crankshaft 30 protrudes rearward from the crank chamber of the crankshaft 30. The drive sprocket 30s is formed on the side portion, and a primary drive gear 56a is provided on the rear end portion thereof via a fluid coupling 55 that is a fluid coupling.

The fluid coupling 55 includes a pump impeller 55p fixed to the crankshaft 30, a turbine runner 55t facing the pump impeller 55p, and a stator 53s .
The primary drive gear 56a is coupled to a turbine runner 55t that can rotate with respect to the crankshaft 30, and the power from the crankshaft 30 is transmitted to the primary drive gear 56a via hydraulic oil.
The primary drive gear 56a meshes with a primary driven gear 56b that is supported by the main shaft 61, which will be described later, and transmits the rotation of the crankshaft 30 to the main shaft 61 side.

On the other hand, a starting driven gear 59 is pivotally supported on the front side portion of the crankshaft 30 protruding forward from the crank chamber C via an AC generator 57 and a one-way clutch 58.
A balancer shaft driving gear 54 is fitted to a portion of the crankshaft 30 along the inner surface of the front wall of the crank chamber C.

A transmission chamber M is formed by a partition wall on the left side of the crank chamber C that houses the crank web 30w of the crankshaft 30.
The transmission gear mechanism 60 accommodated in the transmission chamber M is a constantly meshing gear mechanism, and a main shaft 61 is pivotally supported on the upper crankcase 31U at an obliquely upper position on the left side of the crankshaft 30. A counter shaft 71 is pivotally supported by being sandwiched between the split surfaces of the upper and lower crankcases 31U and 31L at a position diagonally downward to the left of 61 and to the left of the crankshaft 30 (see FIG. 3).

  The main shaft 61 includes an inner cylinder 61i and an outer cylinder 61o that is rotatably fitted to a part of the inner cylinder 61i. The front end of the inner cylinder 61i is formed on the front side wall 31f of the transmission chamber M of the upper crankcase 31U. The bearing recess 62 is rotatably supported via a bearing 62b, and an outer cylinder 61o is fitted in a substantially central position on the rear side of the inner cylinder 61i so as to be relatively rotatable. The portion is rotatably supported by a bearing opening 63 formed in the rear side wall 31r of the transmission chamber M via a bearing 63b, and is supported together with the inner cylinder 61i.

In the outer cylinder 61o, the second speed change drive gear m2 and the fourth speed change drive gear m4 are integrally formed on the inner side of the bearing 63b in the front and rear, and a part of the outer side of the outer cylinder 61o protrudes outward from the bearing 63b.
The inner cylinder 61i is integrally formed with the first transmission driving idle gear m1 and the shifter in order from the front in front of the second and fourth transmission driving gears m2 and m4 of the outer cylinder 61o and is spline-fitted to the inner cylinder 61i. A fifth transmission drive gear m5 and a third transmission drive idle gear m3 are pivotally supported, and an outer portion of the inner cylinder 61i protrudes further rearward than the outer portion of the outer cylinder 61o.

  The bearing recess 62 formed in the front side wall 31f has a small inner diameter so as to support the front end of the small-diameter inner cylinder 61i, whereas the bearing opening 63 formed in the rear side wall 31r has a maximum diameter. It has an inner diameter smaller than that of the fifth transmission drive gear m5 but larger than the diameter of the fourth transmission drive gear m4, and is used for assembling the main shaft 61.

An input sleeve 65 is rotatably fitted to the outer portion of the inner cylinder 61i along with the outer cylinder 61o, and the primary driven gear 56b is fitted to the center of the input sleeve 65, and the primary driven gear 56b is cranked. It meshes with the primary drive gear 56a on the shaft 30 side.
A first transmission clutch 66 is assembled to the rear of the input sleeve 65 from the primary driven gear 56b, and a second transmission clutch 67 is assembled to the front of the primary driven gear 56b.

The pair of first transmission clutch 66 and second transmission clutch 67 are hydraulic multi-plate friction clutches having the same structure.
In the first transmission clutch 66, a hook-like clutch outer 66o opened rearward is integrally fitted to the input sleeve 65, and a clutch inner 66i is integrally fitted to the inner cylinder 61i.
On the other hand, in the second transmission clutch 67, a hook-like clutch outer 67o that opens forward is integrally fitted to the input sleeve 65, and a clutch inner 67i is integrally fitted to the outer portion of the outer cylinder 61o.

  When hydraulic pressure is supplied to the first transmission clutch 66 and the clutch outer 66o and the clutch inner 66i are connected, the rotation of the input sleeve 65 integral with the primary driven gear 56b is rotated by the second and fourth speed change drive gears m2, When the hydraulic pressure is not supplied to the rotation of m4, the clutch outer 66o and the clutch inner 66i are disconnected, and the rotation is not transmitted to the second and fourth speed change drive gears m2 and m4 of the outer cylinder 61o.

  Similarly, when hydraulic pressure is supplied to the second transmission clutch 67 and the clutch outer 67o and the clutch inner 67i are connected, the rotation of the input sleeve 65 integral with the primary driven gear 56b is transmitted to the inner cylinder 61i and is transmitted to the inner cylinder 61i. When the fifth transmission drive gear m5 fitted with the spline is rotated and no hydraulic pressure is supplied, the clutch outer 67o and the clutch inner 67i are disconnected, and the rotation is not transmitted to the fifth transmission drive gear m5 on the inner cylinder 61i.

The counter shaft 71 pivotally supported between the upper and lower crankcases 31U and 31L at a diagonally lower position on the left side of the main shaft 61 as described above has a front side portion on the front side wall 31f of the mission chamber M. The formed bearing opening 72 is rotatably supported via a bearing 72b, and the rear end is rotatably supported by a bearing recess 73 formed in the rear side wall 31r of the transmission chamber M via a bearing 73b. Be supported.

A third shift driven gear n3 integrally formed with the first shift driven gear n1, the fifth shift driven idle gear n5, and the shifter in order from the front side in the transmission chamber M in the mission chamber M is spline-fitted to the counter shaft 71. The reverse idle gear nR, the second shift driven idle gear n2, the shifter nS, and the fourth shift driven idle gear n4 are pivotally arranged.
The corresponding shift drive gear and shift driven gear are always meshed.

  A reverse idle shaft 70 is disposed above the counter shaft 71 (see FIGS. 3 and 4), and a reverse large-diameter gear r1 and a reverse small-diameter gear r2 are integrally rotatable on the reverse idle shaft 70. The reverse large-diameter gear r1 is engaged with the second speed change drive gear m2 on the main shaft 61, and the reverse small-diameter gear r2 is engaged with the reverse idle gear nR on the counter shaft 71.

The fifth shift drive gear m5 on the main shaft 61 and the third shift driven gear n3 on the counter shaft 71 are shifter gears, and the two shifter gears and the shifter nS are moved in the axial direction by the shift drive mechanism and shifted to the shift stage. Is configured.
That is, the fifth speed drive gear m5 moves forward and backward to form the first speed and the third speed, the third speed driven gear n3 moves forward and backward to form the fifth speed and reverse, and the shifter nS moves back and forth to the second speed. A stage and a fourth speed stage are configured.
This gear shift control and the control of the first shift clutch 66 and the second shift clutch 67 are combined to transmit power to each shift step.

The front end of the counter shaft 71 protrudes forward from the bearing 72b, and an output gear 74 is spline-fitted to the front end.
The output shaft 80 is disposed obliquely right below the counter shaft 71 (see FIG. 3), and a driven gear 75 that is spline-fitted to the front portion of the output shaft 80 is connected to the front end of the counter shaft 71. The power is transmitted from the counter shaft 71 to the output shaft 80 by meshing with the output gear 74.

Since a large load is applied to the output gear 74 at the front end of the counter shaft 71 by meshing with the driven gear 75 of the output shaft 80, a bearing 72b that supports the front portion of the counter shaft 71 is configured using a relatively large one. ing.
Therefore, the inner diameter of the bearing opening 72 that fits the bearing 72b in the front side wall 31f is increased, but the bearing recess 62 of the adjacent main shaft 61 is formed with a small diameter as described above. The strength of the front side wall 31f of the crankcase 31 can be maintained high.

  A front case cover 85, which is a case member, is put on the front surface of the counter shaft 71 and the output shaft 80 of the upper and lower crankcases 31U and 31L, which are divided in the vertical direction, over the split surface. A rear case cover, which is a case member, covers the fluid coupling 55 at the rear end of the crankshaft 30 and the first and second transmission clutches 66 and 67 at the rear end of the main shaft 61 across the split surface on the rear surface of 31L. 150 is covered through a spacer 110 which is also a case member.

  The output shaft 80 is configured by connecting a forged-formed front end bearing portion 81 and a rear end bearing portion 82 to a hollow cylindrical member 83, and the front end bearing portion 81 is formed on the front case cover 85. The bearing 86b is inserted into the bearing opening 86 so that the front end protrudes forward, and the rear end supported portion 82 is supported by the bearing opening 111 formed in the spacer 110. It is pivotally supported by protruding backward.

That is, the output shaft 80 is rotatably supported by the front case cover 85 and the spacer 110, respectively, with the front end bearing portion 81 and the rear end bearing portion 82 protruding front and rear.
The front end supported portion 81 of the output shaft 80 passes through a through hole 76f formed in the front side wall of the lower crankcase 31L, and the rear end supported portion 82 is formed on the rear side wall of the lower crankcase 31L. It penetrates the through hole 76r.
The front through hole 76f is adjacent to the front bearing opening 72 of the counter shaft 71, and the rear through hole 76r is adjacent to the rear bearing opening 73 of the counter shaft 71.

The driven gear 75 is spline fitted to the front end bearing portion 81 adjacent to the inside of the bearing 85b.
Accordingly, the output gear 74 at the front end of the counter shaft 71 is engaged with the driven gear 75 that is spline-fitted to the front end bearing portion 81 of the output shaft 80, and power is transmitted from the counter shaft 71 to the output shaft 80.

  The output shaft 80 is configured by connecting a forged molded front end bearing portion 81 and a rear end bearing portion 82 with a hollow cylindrical member 83, so the output shaft 80 is lightened while ensuring rigidity and strength. In addition, the forging device can be reduced in size and the equipment cost can be reduced as compared with the conventional method forging the entire output shaft.

  A front end bearing portion 81 and a rear end bearing portion 82 at both ends of the output shaft are respectively connected to the front case cover 85 and the spacer 110 connected to the front and rear sides in the crankshaft direction of the vertically divided crankcases 31U and 31L. Since it is pivotally supported via 111b, the load on the crankcases 31U and 31L is reduced, and the hollow cylindrical member 83 is configured to be long by separating the front end bearing portion 81 and the rear end bearing portion 82 from each other. In this structure, distortion of one of the output shafts hardly affects the other.

A through hole 76f adjacent to the bearing opening 72 of the countershaft 71 in the lower crankcase 31L,
Since the output shaft 80 penetrates 76r, the output shaft 80 can be brought as close as possible to the counter shaft 71, and the power unit P can be downsized.

  Even when the output shaft 80 is brought close to the counter shaft 71, the counter shaft 71 is pivotally supported by the front case cover 85 while the counter shaft 71 is pivotally supported by the crankcases 31U and 31L. And the rigidity of the bearing portions of both the output shaft 80 and the counter shaft 71 and the output shaft 80 can be both well supported.

On the other hand, a balancer shaft 90 is pivotally supported between the split surfaces of the upper and lower crankcases 31U and 31L at the right side of the crankshaft 30 (see FIG. 3).
Referring to FIG. 5, the balancer shaft 90 includes bearings 91b and 92b in bearing openings 91 and 92 formed at the front and rear side walls of the upper and lower crankcases 31U and 31L, respectively. Thus, it is pivotally supported.

  The balancer shaft 90 is arranged as close to the crankshaft 30 as possible. As shown in FIG. 5, the balancer weight 90w of the balancer shaft 90 is connected to the crank web 30w of the crankshaft 30 in the crankshaft direction (front-rear direction). (The counter weight) and the positional relationship.

A driven gear 93 is spline-fitted adjacent to a bearing 91b fitted to the front end of the balancer shaft 90 on the inside, and the driven gear 93 is connected to the balancer shaft driving gear 54 fitted to the crankshaft 30. The rotation of the crankshaft 30 is transmitted to the balancer shaft 90 at the same rotational speed.
Therefore, the primary vibration caused by the reciprocating motion of the piston 40 is canceled by the rotation of the balancer shaft 90 at the same speed as the crankshaft 30.

  A water pump 95 provided on a front cover member 87 that covers the AC generator 57 and the like from the front is disposed in front of the balancer shaft 90, and is freely rotatable on a bearing tube portion 87a of the front cover member 87. A pivotally supported water pump drive shaft 96 is arranged coaxially with the balancer shaft 90.

Then, a connecting convex portion 90f protruding forward from the front end of the balancer shaft 90 and a connecting concave portion 96a formed at the rear end of the water pump drive shaft 96 are fitted, and the rotation of the balancer shaft 90 is transmitted to the water pump drive shaft 96. Then, the water pump 95 is driven.
A water pump cover 97 having a suction cylinder 97a is put on the front side of the water pump 95.
The suction cylinder 97a of the water pump cover 97 is connected to the radiator 27 disposed in front of the vehicle body by a water pipe, and the water pump 95 sucks cooling water from the radiator 27.

  On the other hand, an oil pump unit 100 provided in the spacer 110 is disposed behind the balancer shaft 90, and an oil pump drive shaft 101 rotatably supported by the oil pump unit 100 is connected to the balancer shaft. It is arranged coaxially with 90.

  Then, a connecting recess 90r formed at the rear end of the balancer shaft 90 and a connecting projection 101a protruding at the front end of the oil pump drive shaft 101 are fitted, and the rotation of the balancer shaft 90 is transmitted to the oil pump drive shaft 101 to be The pump unit 100 is driven.

  The lubrication of the power unit P employs a dry sump method, and the oil pump drive shaft 101 in the oil pump unit 100 has a structure in which each of the scavenge pump 102 and the feed pump 103 rotor is attached.

A shift drive mechanism 200 that shifts by moving a shifter of the transmission gear mechanism 60 of the transmission T is provided below the crankshaft 30 and the main shaft 61.
A gear case portion is formed in the lower part of the rear case cover 150. The gear case cover 201 is covered from behind, and a reduction gear mechanism is provided therein. A gear transmission motor 202 is provided on the right side of the gear case cover 201 from the rear. The shift spindle 206 is attached to the lower left portion of the gear case cover 201 through the front case cover 85, the front and rear walls of the lower crankcase 31L, the rear case cover 150, and a rear end hexagonal column-shaped engaging portion 206a. It is arranged to protrude rearward (see FIGS. 3 and 6).
An angle sensor 207 fixed to the front case cover 85 is attached to the front end of the shift spindle 206.

A first idle gear shaft 203 and a second idle gear shaft 204 are rotatably supported in the gear case, and a small-diameter drive gear 202a formed on a motor drive shaft protruding forward from the gear cover 201 of the speed change electric motor 202. Meshes with a large-diameter gear 203a integral with the first idle gear shaft 203, and a small-diameter gear 203b integral with the first idle gear shaft 203 meshes with a large-diameter gear 204a integral with the second idle gear shaft 204. A reduction gear mechanism is configured by a small-diameter gear 204b integrated with the second idle gear shaft 204 meshing with a fan-shaped gear shift arm 205 fitted to the shift spindle 206.
Accordingly, the drive of the speed change electric motor 202 is decelerated via the reduction gear mechanism to rotate the shift spindle 206.

  Between the front and rear walls of the lower crankcase 31L, a shift drum 210 is rotatably supported obliquely above the shift spindle 206, and a shift transmission means 208 is interposed between the shift spindle 206 and the shift drum 210. The rotation of the shift spindle 111 rotates the shift drum 210 via the shift transmission means 208.

As shown in FIG. 6, the shift pins of the shift forks 215a, 215b, and 215c that are slidably supported by the guide shaft 215 are fitted into the three shift grooves formed on the outer peripheral surface of the shift drum 210. The shift fork 215a that is guided in the shift groove by the rotation of the shift drum 210 and moves in the axial direction moves the shifter gear (fifth shift drive gear m5) on the main shaft 61, and the shift forks 215b and 215c are counter shafts. The shifter gear (third shift driven gear n3) on 71 and the shifter nS are moved to change the set of gears engaged with each other to perform a shift.
The rotation angle of the shift drum 210 is detected by a shift position detector 211 provided coaxially in front of the shift drum 210.

  The drive of the speed change electric motor 202 by the speed change drive mechanism 200 rotates the shift spindle 206 via the reduction gear mechanism, and the rotation of the shift spindle 206 rotates the shift drum 210 via the shift transmission means 208. The shift forks 215a, 215b, and 215c are moved by the rotation of the shift drum 210 to change the speed.

  Further, a hexagonal column engaging portion 111a of the shift spindle 206 protruding rearward from the gear case cover 201 is engaged with a hexagonal hole acting portion of a wrench that is a rotating operation tool, along the surface of the rear case cover 150. By performing the rotation operation, the shift spindle 206 can be rotated to manually execute a shift.

  Here, the shift spindle 206 is formed with a large diameter because the rear half 206r from the rear case cover 150 to the rear wall of the lower crankcase 31L is a power transmission portion, whereas the front half 206f is Since the load of power transmission is not applied, it has a small diameter.

The rear half 206r is pivotally supported by the gear case cover 201 and the rear case cover 150 via bearings 209a and 209b, and is also pivotally supported by the rear wall of the lower crankcase 31L.
The small-diameter front half 206f has a structure in which only the supported portions 206fa and 206fb that are pivotally supported by the front wall of the lower crankcase 31L and the front case cover 85 via bearings 209c are expanded.
In this way, weight reduction is achieved by forming the front half 206f, which does not apply a load of power transmission only by operating the angle sensor 207, with a small diameter.

A modification of the shift spindle 206 is shown in FIG.
This speed change drive mechanism is the same as the example shown in FIG. 6 except for the shift spindle 230, and uses the same reference numerals.

  This shift spindle 230 has a structure in which a cylindrical member 232 is connected between a front end supported part 231 and a rear half member 233, and the front end supported part 231 is pivotally supported by a front case cover 85, A certain rear half member 233 is substantially the same as the rear half portion 206r of the shift spindle 206 and is pivotally supported by the rear wall of the lower crankcase 31L and the rear case cover 150.

A cylindrical member 232 connects the front end supported part 231 and the rear half member 233 through the front wall of the lower crankcase 31L.
The portion where the load of power transmission is not applied is reduced in weight as the cylindrical member 232.

FIG. 8 shows still another modification of the shift spindle.
This shift spindle 250 is configured by coaxially connecting a front half member 251 and a rear half member 252. The rear half member 252 serving as a power transmission unit has a large diameter, and the front half member 251 to which no load of power transmission is applied is configured with a small diameter. Yes.

The rear end of the small-diameter front half member 251 is inserted into a shaft hole drilled in the front end surface of the large-diameter rear half member 252 and both are connected by a pin 253 inserted in the diameter direction.
By reducing the diameter of the first half member 251 to which no load of power transmission is applied, weight reduction is achieved.

It is a side view of the state which removed the body cover etc. of the rough terrain vehicle in which the power unit concerning one embodiment of the present invention was carried. It is the same top view. It is a rear view of the power unit. It is an expanded sectional view (IV-IV line sectional view of Drawing 3) of the power unit. It is sectional drawing (VV line of FIG. 3, V'-V 'line sectional drawing) of the power unit. It is an expanded sectional view of a speed change drive mechanism. It is an expanded sectional view of a speed change drive mechanism of another modification. FIG. 10 is a developed cross-sectional view of a speed change drive mechanism of still another modified example.

Explanation of symbols

P: power unit, E: internal combustion engine, T: transmission,
1 ... Rough terrain vehicle,
30 ... crankshaft, 31L ... lower crankcase, 31U ... upper crankcase,
60 ... transmission gear mechanism, 61 ... main shaft, 70 ... reverse idle shaft , 71 ... counter shaft, 72 ... bearing opening, 72b ... bearing, 73 ... bearing recess, 73b ... bearing, 74 ... output gear, 75 ... driven gear,
80 ... output shaft, 81 ... front end supported part, 82 ... rear end supported part, 83 ... hollow cylindrical member,
85 ... Front case cover, 86 ... Bearing opening, 86b ... Bearing, 90 ... Balancer shaft,
110 ... Spacer, 111 ... Bearing opening, 111b ... Bearing,
200: transmission drive mechanism, 202: electric motor for transmission, 206 shift spindle, 210: shift drum, 230: shift spindle, 250: shift spindle.

Claims (4)

The output shaft of the power unit (P) that has a driven gear (75) that inputs the power of the internal combustion engine (E) of the power unit (P) through the transmission mechanism (T) and outputs the power to the outside of the unit case (P) ( 80)
Bearing unit members (81, 82) at both ends that are rotatably supported via bearings in the unit case (31) are forged, respectively.
The bearing members (81, 82) at both ends are connected by a cylindrical member (83),
An output shaft of a power unit, wherein the driven gear (75) is fitted to one of the supported members (81) adjacent to the bearing (86b). The bearing member (81, 82) has a flange formed at a predetermined position on the outer peripheral surface,
  One of the bearing members (81) is positioned by being fitted into the driven gear (75) and the bearing (86b) from the inside and the collar portion is in contact with the driven gear (75),
  The output shaft of the power unit, wherein the other supported member (82) is fitted into the bearing (111b) from the inside, and the collar portion is positioned in contact with the bearing (111b). The unit case (31) includes a vertically divided crankcase (31U, 31L) and both case members (85, 150) connected to both outer sides in the crankshaft direction of the crankcase (31L, 31R),
Across each of the bearing members (81, 82) of the bearing of the output shaft to each of the two case members (85,150) (80) (85b , 111b) according to claim 1 or characterized in that it is rotatably supported via a The output shaft of the power unit according to claim 2 . The power unit (P) is mounted on the vehicle with the crankshaft (30) oriented in the front-rear direction,
A through-hole (76f) through which the output shaft (80) passes adjacent to the bearing portion of the transmission shaft (71) pivotally supported by the crankcase (31U, 31L) has the vertically split crankcase (31U, The output shaft of the power unit according to claim 3 , wherein the output shaft is formed in one crankcase (31L) of 31L).

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